N. Gruhler et al.: Diamond on aluminium nitride as a platform for integrated photonic circuits, Phys. Stat. Sol A (2016) vol. 213, issue 8, pages 207-2080 discloses to deposit a polycrystalline diamond layer heteroepitaxially from the gas phase and to subsequently produce waveguides made of diamond as part of integrated optical components by structuring and etching.
However, the strong attenuation of optical signals resulting from the large number of crystal defects of the polycrystalline diamond is disadvantageous in connection with this known optical component. Therefore, waveguides of integrated optical components are produced from other materials, e.g. SiO2, ZnSe or Ge, for technical applications. However, these materials have the drawback that the refractive index is considerably lower than in the case of diamond. Furthermore, the band gaps of these materials are considerably smaller, such that light of shorter wavelengths is strongly absorbed on account of the generation of electron-hole pairs. Finally, the heating also leads to the generation of free charge carriers, as a result of which the known materials also lose their transparency to infrared light at high temperatures.